You have to think that the Eagles will put Nnamdi Asomugha one on one with Wallace for a good portion of the game, and maybe mix in some Rodgers-Cromartie as well depending on how the Steelers lineup. If they move him, NA, around then he'd go up against Antonio Brown and then the Eagles could roll an extra coverage man over to help out on either side.
Leaving both AB and Wallace alone one on one all day is risky but if they find themselves able to cover both guys in that manner it could be trouble since that frees up an extra player in the pass rush.
This will be an interesting matchup; the first time this season that Wallace will potentially have an elite corner covering all game long. Does he win those battles? Does Ben even go after him very much?
Ben has never been the type to shy away from any DB so I expect he'll take some shots to whoever NA is covering but I wouldn't expect him to go that way all day long unless he has early success.